A method and a device for controlling an internal combustion engine are described in published German patent document DE 103 05 656, in which a manipulated variable of an actuator is computed based on the comparison of a variable characterizing the combustion process in at least one cylinder to a setpoint value for this variable, for influencing at least one additional manipulated variable. The output signal from a structure-borne noise sensor is used to generate the variable. Based on the signal from the structure-borne noise sensor, a feature is obtained there which is adjusted to a predetermined setpoint value. Cylinder-specific variables which characterize the combustion process in at least one cylinder may also be obtained based on a combustion chamber pressure sensor.
Various characteristics which characterize the combustion process in at least one cylinder may be obtained and used for regulation, based on a structure-borne noise sensor and/or a combustion chamber pressure sensor.
Homogeneous and/or partially homogeneous combustion processes are characterized by a high exhaust gas recirculation rate in combination with injection, modified with respect to conventional combustion, for achieving a high ignition delay. These combustion processes are usually used only in partial regions of the engine characteristics map, in addition to the conventional combustion process. Low emissions, in particular of nitrogen oxides and particulates, occur in homogeneous combustion processes.
However, these homogeneous combustion processes exhibit high sensitivity in particular to tolerances in cylinder filling, which is defined by the air-fuel ratio. Therefore, the advantages in controlled operation are not fully realized, or are not realized at all. Furthermore, it is problematic that the control units for controlling and/or regulating cylinder filling are generally not designed for individual cylinders. It is also common to control the transition between the various operating modes, i.e., the transition between conventional and homogeneous combustion.
An object of the present invention is to reduce the sensitivity of the homogeneous combustion process with respect to tolerances in cylinder filling in both steady-state and dynamic operation, within the homogeneous operating mode as well as during changes in operating mode.